Morphogenesis of multicellular organisms requires the synthesis and assembly of complex extracellular structures. Although several extracellular proteins have been identified, little is known about how these proteins actually function to produce organized macromolecular structures. The long-term goals of this proposal are to understand how extracellular proteins assemble into-macromolecular complexes and how these complexes function in morphogenesis. The most abundant and ubiquitous extracellular proteins are the collagens. Several human connective tissue disorders have been shown to result from mutations in collagens, but no simple animal model for studying collagen defects has been available. Mutations in two collagen genes in the nematode C.elegans, have been shown to cause severe defects in organisms morphology. The powerful genetic and molecular analyses that are possible in C.elegans, and its simple anatomy, make it an excellent model system for studying the functions of collagens. Mutations in the two collagen genes of C. elegans alter the structure of the cuticle (exoskeleton) and the morphology of the organism. Different mutations in these collagen genes have different genetic properties and can cause very different morphological defects. The molecular alterations in five mutant alleles of these genes have been determined. Additional mutant alleles will be generated so that the genetic and molecular properties of further collagen defects can be examined. The effects of defined mutations will be analyzed by creating transgenic strains carrying in vitro mutagenized collagen genes. Antibodies specific for the sqt-l and rol-6 collagens will be produced and utilized to analyze the steps of assembly of wild-type and mutant collagens into the cuticle. Alterations in the structure of mutant cuticles will be analyzed by electrorunicroscopy, utilizing the specific antisera. The sqt-l and rol-6 genes have been shown to interact genetically with other genes that affect organismal morphology. These interacting genes are likely to encode proteins that interact physically with the sqt-l and rol-6 collagens. Interacting genes will be further characterized genetically and the effects of mutations in these genes on the assembly and function of the sqt-l and rol-6 collagens will be analyzed. These studies will provide insights into the genetic and molecular properties of collagens, and their roles in morphogenesis.